For House Marik probably 1st Free World Guard, Marik Gunfighter Alliance and Midgard Inc.
There have been some more additions to House Marik like (Mercstar) and molten metal militia BUT those recently changed and have a history of faction hopping for whatever reason

IDI is an EU unit and will be Davion loyalist for a while yet..... but major player with 8-10 active players? Nah, we're just here for the schnapps and giggles.... oh and fine hair grooming products. This beard doesn't look after itself you know